USEFUL SOFTWARE | Free, Open Source, Commercial

[BAndrew]

• Notepad++ - A source code editor written in C++. Extremely useful for programming/scripting. | Free | Windows
  
• LibreOffice - An alternative for Microsoft Office | Free/Open Source | Windows + Linux + Mac OS X (x86_64 10.8 or newer required)
  
• TeXstudio - An integrated writing environment for creating LaTeX documents (mainly for scientific/academic or work purposes) | Free/Open Source |Windows + Linux + Mac OS X (version 10.8+)
  
• Mozilla Thunderbird - A free email management application | Free | Windows + Linux
  
• FileZilla - FTP client and server | Free/Open Source | Supports all platforms for the client and windows for the server.